This invention relates to polymeric compositions suitable for use as antioxidant dispersants for lubricating oil and/or additives for fuels for internal combustion engines, particularly compositions which are compatible with synthetic rubbers and other polymeric materials utilized in seals and the like within internal combustion engines.
Internal combustion engines operate under a wide range of temperatures including low temperature stop-and-go service as well as high temperature conditions produced by continuous high speed driving. Stop-and-go driving, particularly during cold, damp weather conditions, leads to the formation of a sludge in the crankcase and in the oil passages of a gasoline or a diesel engine. This sludge seriously limits the ability of the crankcase oil to effectively lubricate the engine. In addition, the sludge with its entrapped water tends to contribute to rust formation in the engine. These problems tend to be aggravated by the manufacturer's lubrication service recommendations which specify extended oil drain intervals.
It is known to employ nitrogen containing dispersants and/or detergents in the formulation of crankcase lubricating oil compositions. Many of the known dispersant/detergent compounds are based on the reaction of an alkenylsuccinic acid or anhydride with an amine or polyamine to produce an alkenylsuccinimide or an alkenylsuccinamic acid as determined by selected conditions of reaction.
It is also known to chlorinate alkenylsuccinic acid or anhydride prior to the reaction with an amine or polyamine in order to produce a reaction product in which a portion of the amine or polyamine is attached directly to the alkenyl radical of the alkenylsuccinic acid or anhydride. The thrust of many of these processes is to produce a product having a relatively high level of nitrogen in order to provide improved dispersancy in a crankcase lubricating oil composition.
With the introduction of four cylinder internal combustion engines which must operate at relatively higher engine speeds or RPM's than conventional 6 and 8-cylinder engines in order to produce the required torque output, it has become increasingly difficult to provide a satisfactory dispersant lubricating oil composition.
Another problem facing the lubricant manufacturer is that of seal deterioration in the engine. All internal combustion engines use elastomer seals, such as Viton.RTM. seals, in their assembly. Over time, these seals are susceptible to serious deterioration caused by the lubricating oil composition. A lubricating oil composition that degrades the elastomer seals in an engine is unacceptable to engine manufacturers and has limited value.
An important property of a lubricating oil additive and a blended lubricating oil composition containing such additives is the compatibility of the oil composition with the rubber or elastomer seals employed in the engine. Nitrogen-containing succinimide dispersants employed in crankcase lubricating oil compositions typically have the effect of seriously degrading the rubber seals in internal combustion engines. In particular, such dispersants are known to attack Viton.RTM. AK-6 rubber seals. This deterioration exhibits itself by sharply degrading the flexibility of the seals and increasing their hardness. This is such a critical problem that Volkswagen Corporation requires that all crankcase lubricating oils must pass a Viton.RTM. Seal Compatibility Test before the oil composition will be rated acceptable for engine crankcase service. The polymeric dispersants of the present invention exhibit improved Viton.RTM. seal compatibility over prior art additives. (Viton.RTM. is the trademark for a series of fluoroelastomers based on copolymers of vinylidene fluoride and hexafluoropropylene, produced by DuPont de Nemours, E. I. & Co of Wilmington, Del.).
It is an object of this invention to provide an improved antioxidant-dispersant lubricating oil additive.
Another object is to provide a novel lubricating oil composition which does not degrade elastomer seals in internal combustion engines.
A still further object is to provide a lubricating oil composition which can withstand the stresses imposed by modern internal combustion engines.
Other objects and advantages of the present invention will be apparent to those skilled in the art from a perusal of the following disclosure, including the appended claims.